Twin wire paper forming with one wire wrapping a suction cylinder

ABSTRACT

Apparatus for forming a fibrous web wherein a headbox discharges fibrous suspension between a first endless forming wire and a second endless forming wire which together form a nip upstream of a suction cylinder. The first wire wraps around a large portion of the surface of the suction cylinder whereas the second wire proceeds with the first wire around only a portion of the suction cylinder. An endless felt is supported to wrap around the suction cylinder in conjunction with the first wire downstream of the second wire to press and dewater the web. At least one suction box is positioned adjacent the second wire upstream of the suction cylinder, and a pressing mat employed in conjunction with a pressure box may be provides adjacent the suction cylinder for applying pressure to the felt as it wraps the suction cylinder.

July 16, 1974 P. NEVALAINEN 3,824,152

TWIN WIRE PAPER FORMING WITH ONE WIRE WRAPPING A SUCTION CYCLINDER Filed larch 21, 1973 WIRE PAPER FORMING WITH ONE WIRE WRAPPING A" SUCTION CYLINDER entti Nevalainen Kai-hula, Finland, assignor to Alilstrornv Osakeyhtio, .Noor rnarkku, Finland Filed MarCZl 1973, Ser. No. 343,401

mi ation Finland, Mar. 24, 1972,

Int, Cl. D21f 1/00, 2/00 301 Claims BSTRACT OF "THE DISCLOSURE ,Apparaftus fornformin'g'a 'fibrous'web wherein a headbox discharges Zfibrous .suspension:between a first endless forming-wire anda-asecond endless forming wire which togetherform as-niptupstream of a suction cylinder. The first-wireiwraps around a largeportion of the surface of the-fsuction:tcyliirderzz whereas the second wire proceeds withitheyfirst wiretaroundonly arportion of the suction cylinder. An endless felt is supported to wrap around the suctiomcylinder insconjunction with" the first wire downstream'of thesecond wire-to press and dewater the web. At least OHETSUCIIOIIIJOX is positioned adjacent the second wireupstream pfthesuctioncylinder, and a pressing mat employed in conjunction with a pressure box may be provided adjacent the suction cylinder for applying pres sure, to'tthe'gfelt as r it Twraps the suction cylinder.

BACKGROU- I D OF THE INVENTION Field of the Invention igThe presentsinventionrelates to an apparatus for forming a fiber web and-including asuction cylinder provided oneor more suction Zones toremove water from the fiber-web "and -Wiresor similar supporting means for the web running through the apparatus.

Description of the Prior Art Several apparatuses ofthe abovetype for forming fiber webs are known previoiislybhesuch known apparatus for forming a fiber web has two endlss'wires which work in conjunction with each other and which have been fitted to run over a part of the surface of the suction cylinder, while fiber suspension is fed between the wires at a point before the suction cylinder. Then the fiber web is moved along that part of the suction cylinder including the suction zone so that part of the water is sucked into the suction cylinder while another part of the water is pressed from the fiber web through the outer wire. Finally the wires are guided away from the suction cylinder surface and each other, the fiber web remaining on one of the wires. The use of wires is especially advantageous when the intention is to quickly remove great amounts of water from the web, because the wire will not be clogged by the fibers and the filler removed along with the water. In addition, to make the removal of water more effective, the outer wire has been pressed against the fiber web between the wires by fitting pressing rollers against that surface of the outer wire which faces away from the web.

The disadvantage of these apparatuses for forming a fiber web is the deep impressions left by the wires on the fiber web. These impressions are especially disturbing if pressing means is used. 1

Such apparatuses for forming fiber web are also known in which one of the wires has been replaced by a felt. If the inner wire surrounding the suction cylinder is replaced by a felt, the felt is quickly clogged and removal of water into the suction cylinder becomes difficult or ceases completely, and if the outer wire is replaced by a felt, two-sided removal of water, which is important United States Patent 0 3,824,152 Patented July 16, 1974 for web formation, is no longer possible because the outer felt is quickly clogged by the relatively large amounts of water removed through it at the initial stage of the web formation.

It is an object of the present invention to provide a web forming apparatus wherein the disadvantages described above have been essentially eliminated.

SUMMARY OF THE INVENTION The present invention provides an apparatus of the character once described, comprising an endless first wire running over the suction zones of the suction cylinder to prevent the fibers from being sucked into the cylinder, a second endless wire running along part of the suction cylinder and constituting together with said first wire a forming zone for the fiber web, and an endless felt running along part of the suction cylinder and constituting together with the first wire a pressing zone for the fiber web, said pressing zone following immediately after the forming zone. I

. The problems connected with wires and felts have thus been solved according to the invention by dividing the outer supporting means into two parts, the first of which is an endless wire and the other one an endless felt. In this manner great amounts of water can be removed from the fiber web to both of its sides at the initial stage of web formation without risk of clogging, and at the final stage of web formation, when only small amounts of water escape from the web, the fiber web is pressed with the help of the felt against the endless wire which surrounds the suction cylinder, in which case that side of the fiber Web which faces the felt still remains relatively even. Removal of water is especially effective when suction boxes removing water in a direction opposite to that of the suction cylinder are fitted on that side of the outer wire which faces away from the fiber web and at a point before the suction cylinder. Two-sided removal of water, so important for web formation, is thereby obtained. In addition, to make the removal of water more eflective, pressing means can be fitted inside the felt loop to press the felt against the fiber web. In an apparatus according to the invention, the removal of water takes BRIEF DESCRIPTION OF THE DRAWING The enclosed drawing shows a schematic side view of a specific embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, numbers 1 and 2 indicate endless wires, 3 a head box, 4 a suction cylinder with suction zones I, II, and III, and 5, 6 refers to a pressing roller combination which forms a so-called extended nip with suction cylinder 4. An endless mat 19, which is pressed against the suction cylinder by the overpressure provided in box 20, runs around the pressing rollers. Number 7 refers to a turning roller (suction) which together with roller 8 forms a first press. Numbers 9, 10, and 11 indicate the guide rollers of wire 1, number 12 indicates the endless felt, and 13, 14 the pressing rollers; 15 and 16 are waterremoving boxes which are provided with transversal lists to support the wire and can work with suction.

The jets emerging from the lip opening of the head box are fed onto wire 1, where the removal of water takes place through the box 15. The direction of the wire in the area between guide rollers 9 and 10 can be horizontal or tilting downwards, as shown in the figure. Al-

ternatively, the head box may feed the fiber suspension into the convergent space between wires 1 and 2, in which case the guide roller is positioned in the immediate vicinity of the lip. That part of the wire which is between guide rollers 17 and 10 is unsupported but has been tightened so that it can adapt according to the pressure created in the space between the wires.

At guide roller 10 the direction of wires 1 and 2 and the damp web between them changes, at which time water is removed from web 21 by centrifugal force; the Water is flung into container 18. After passing turning roller 10 the wires run together onto cylinder 4 which has been provided with partitions. These have been divided into zones with different pressures. Wire 1 presses the web against the cylinder and runs along the cylinder surface as far as zone II, where guide roller 11 detaches the wire from web 21. i

At the beginning of zone III the felt 12 is guided onto the cylinder and runs along the cylinder surface to the end of the zone. The removal of water in zone III can be made more effective with a pressing roller combination and 6.

The suction roller 7, which is positioned at the end of water removal zone III, detaches the felt 12, the wire 2 and the damp web 21 (which is between them) from the surface of the cylinder and also works as first pressing means. The wire 2 which surrounds the cylinder is detached from the web, and clinging to the felt and supported thereby, the web 21 runs to the pressing nip formed by pressing rollers 13 and 14.

The water removal zones of the cylinder are preferably situated so that zone I begins at position 34 oclock and zone III ends at position 11-12 oclock, whereby the gravity and the pressure work in the same direction.

An apparatus according to the invention can be used for forming paper, carton, cellulose, and other fiber webs and for removing water from them. The apparatus operaates very smoothly because the fiber web is not left exposed as in most known apparatuses.

What is claimed is:

1. In an apparatus for forming a fiber web from pulp discharged from the outlet of a headbox and having a suction cylinder with at least one suction zone for removing water from the web, and wherein the pulp is discharged into the nip between a first endless wire and a second endless wire, said nip being upstream of said suction cylinder, the improvement which comprises said first endless wire wrapped around said cylinder to prevent the fibres from being sucked into the cylinder; said second'endless'wire wrapped around a first part of the suction cylinder and constituting with said first wire a forming zone for the fiber web immediately downstream the headbox outlet; an endless felt, means supporting said endless felt to wrap same around a second part of the suction cylinder tode fine thereabout with said first wire a'pressiri'g zone for the fiber web, said pressing zonebeing-arranged in following relation to said forming zone with respect to the movement of the fiber web; and means operable to press said endless felt against the fiber web in said pressing zone.

2. The improvement according to claim 1 including atf least one suction box positioned upstream in relation to said suction cylinder, and against the side of said second wire opposite to the fiber web.

'3. The improvementaccording towclaim 2 including two suction boxes at theside of the second wire opposite the fiber web, the first suction box being positioned upstream the nip point at which the first and second 'wires meet with the pulp therebetween, and the secondsuction' rollers, and a pressurized box arranged to press said mat against the endless felt.

5. The improvement according to claim- 1 including an additional suction roller positioned in contact with said felt for taking 011 the fiber web from said first wire.

References Cited UNITED STATES PATENTS 3,472,733 10/1969 Holt 162-301 FOREIGN PATENTS 862,446 2/1971 Canada 16" 2 20"3,

s. LEON BASHORE, Primary'Examiner R. H. TUSHIN, Assistant Examiner US. Cl. X.R.

1 wherein said- 

